"There was an idea... called the Avengers Initiative. The idea was to bring together a group of of remarkable people to see if they could become something more. To see if they could work together when we needed them to, to fight the battles that we never could."

Fury informs Stark that his Iron Man persona is assigned to the team, but due to certain conditions, Stark himself is deemed unsuitable. Stark agrees on the condition that Senator Stern present him and Col. Rhodes with their medals for bravery.

"Know this, son of Coul. You and I, we fight for the same cause: the protection of this world. From this day forward, you can count me in as your ally, if... you return the items you have taken from Jane."

Agent Coulson notes Thor's strength while he is in his mortal form, trying to reclaim Mjolnir. After Thor defeats the Destroyer, Thor tells Coulson to consider him an ally to S.H.I.E.L.D., but speeds away before he can be debriefed, indicating that he has been considered for the Avengers Initiative.

"There was an idea, Stark knows this. Called the Avengers Initiative. The idea was to bring together a group of remarkable people, see if they become something more. See if they can work together when we needed them to. To fight the battles that we never could."

Nick Fury assembles the team when an unexpected threat associated with Thor's brother Loki and the Tesseract appears. The team initially have difficulty and refusal to obey each other; for example, Tony Stark is reluctant to working under the command of Captain America, Thor demands that Loki is his responsibility and the team is uncomfortable with the presence of Bruce Banner. When Loki attempts to destroy the team and promote his godlike supremecy to Earth in a public way, the Avengers depart from S.H.I.E.L.D.'s command and rally in defense of New York as it is invaded by the extraterrestrials known as the Chitauri. Captain America takes command of the team and they each work to supress the invasion force. The Hulk beats Loki into submission and Iron Man sends a nuclear weapon fired by the World Security Council into the portal through which the aliens enter Earth and their fleet is destroyed, breaking the neural connection with their ground troops and instantly killing them. The team take Loki as their prisoner and Thor takes both Loki and the Tesseract back to Asgard. The team disbands but agrees to reassemble when another global threat requires their combined efforts.

After the fall of S.H.I.E.L.D. Loki's Scepter fell into the hands of HYDRA. The threat it posed drew the Avengers back together in a desperate worldwide hunt. The Avengers had the financial backing of Tony Stark. Using the former Stark Tower, now renamed Avengers Tower, as their headquarters. After many months they tracked it to a HYDRA research facility run by Wolfgang von Strucker in Sokovia and launched an all out assault to recover it. The Avengers also noted that they were being harassed by two "enhanced" during the operation, but together with Stark's Iron Legion the team soon overthrew the HYDRA soldiers and reclaimed the sceptre. Tony appealed to Thor to have two days to study the alien device before it was relocated to Asgard, which Thor agreed to, and then the team unanimously agreed to celebrate their victory.

Back in New York at Avengers Tower, Tony began to unravel the mysteries of the sceptre. Tony and Bruce Banner discovered that its core held something akin to a powerful computer and deduced that HYDRA had been trying to use it to create artificial intelligence. With this knowledge he had the epiphany that he might be able to provide real adaptive thought to his Iron Legion in what he called his Ultron Program. He and Bruce then left J.A.R.V.I.S. to continue investigating while he rejoined his team for a night of celebration. The party was huge and the Avengers gathered many of their friends for the night. When the revelry had died down, and most of the guests had left, the remaining men took turns trying to lift Mjölnir. This activity was interrupted by the appearance of a wrecked Iron Legion drone. It quickly became apparent that this was being operated by a rogue artificial intelligence, and the name it claimed for itself was "Ultron". Ultron and a number of other Iron Legion drones, then attacked the small group. They rallied and beat it back, but not before one of the Iron Legion made off with the sceptre during the confusion. Thor promptly turned on Stark demanding to know why he had created such a thing, to which Tony pointed out that they needed a way to deal with threats on the scale of the Chitauri.

The Avengers traced Ultron's movements to a salvage yard on the coast of Africa where Ulysses Klaue dealt in the lucrative end of black market trading. So began a three way battle between Klaue's men after Ultron severed his arm, the Avengers, and the Ultron Sentries. Ultron also had the advantage of the pair of enhanced that the Avengers had encountered in Sokovia, the siblings Wanda and Pietro Maximoff. Pietro's speed allowed him to devastate the ranks of Klaue's men, while Wanda ravaged the minds of the Avengers themselves. When she at last reached Banner, her illusions caused him to fly into a rage that he then directed towards the populace of Johannesburg, and then she Ultron and Pietro made their escape. With most of the Avengers out of action fighting their own inner demons, Tony was left to attend to the problem of a rampaging Hulk on his own. He asked Veronica, a shuttle that could deploy numerous pieces of a heavy duty Iron Man armor. Tony in the Hulkbuster Armor afforded him the physical power to subdue the Hulk, but the public relations damage had been done, leaving Bruce in a morose state. Clint Barton took the group to a safehouse to recover, soon revealing that it was actually his family home. There they met Nick Fury, who began reorienting their thinking and fomenting new strategic considerations within the shattered ranks. Banner and Romanoff had both been psychologically scarred by their encounter Wanda and contemplated simply leaving. Tensions ran high between Tony and Steve Rogers, and Thor had been given a glimpse of something very troubling and departed the group to investigate further.

Ultron's plan to use the sceptre to create a final evolutionarily pure form for himself had become clear, and the last piece of that puzzle was with Dr. Helen Cho in South Korea. They raced for Seoul, and found Ultron deep into an attempt to load his consciousness into a new android body. Their interference forced Ultron to flee, but the group managed to separate the android body from the robot before he escaped again, and Stark, and Barton, took it back to New York. Rogers on the other hand, found himself joined by the Maximoff twins on the street of Seoul after Wanda had discovered Ultron's true intent. Romanoff had not been so lucky, and having been rendered unconscious in the confrontation soon found herself imprisoned by Ultron in Sokovia. Once they were back in New York, Stark and Banner bickered over the android body. Stark wanted to load J.A.R.V.I.S. into it, but Banner didn't trust his judgement. The dispute continued until it was interrupted by the arrival of Rogers and the Maximoff twins, whereupon Pietro ended it by simply unplugging the entire system. Then Thor made a surprise appearance and promptly bathed the android in lightning. It awoke in the surge and cast him aside. The Avengers and the Maximoff twins all moved to counter the android but halted when it stopped by a window to gaze out upon the city. It quickly became apparent that the android was no threat, especially fostering trust in Thor when it hefted Mjolnir with ease. The assembled group then compared stories, and Thor reported news of his vision that the energy core of the sceptre had actually contained the Mind Stone, an item of incredible power and one of the legendary Infinity Stones. That gem was now resting in the forehead of the android, which soon began referring to itself as the Vision.

The Avengers and their three allies turned their attention back to Ultron and Sokovia. Banner went alone to extract Romanoff from her prison, and the others faced off against Ultron. While Ultron's plan to divide and exterminate the Avengers had failed, its plans for the human race were about to be fully revealed. Devices planted within the city engaged, drawing a sizeable portion of it into the sky. The assembled heroes, with Banner and Romanoff back amongst them, fought back against the amassed ranks of Ultron's robot legion. James Rhodes, suited up as War Machine, and a recently repaired helicarrier with him, also eventually joined the battle. After clearing most of the Ultron robots from the city now risen above the cloud layer, the heroes began evacuating the trapped populace in personnel transports sent from the helicarrier. Barton was caught under the guns of the Avengers' own quinjet however, with Ultron at the controls, and only the intervention of Pietro saved him. Pietro had saved both Barton and a boy with this final act, but at the cost of his own life when the quinjet's gunfire tore through his chest. The Vision finally confronted Ultron alone after the Hulk had flung the robot from the quinjet. Heavily damaged, Ultron was no match for the android, and fell to the Vision's power. With Ultron's defeat, the group began an inevitable dissolution. The Hulk switched off the quinjet's communications, leaving it to fly him clear of the scene. Thor and Stark each had their own agendas to pursue, with Thor needing to investigate the matter of yet another Infinity Stone coming within reach. Barton meanwhile had a new baby to attend to and left to return to his family.

Despite their losses, the Avengers were also to be born anew. Steve and Romanoff proceeded to a new Avengers facility in New York, and welcomed a new quartet to the fold. They were joined by the Vision, Wanda Maximoff, James Rhodes aka War Machine, and Steve's recent companion, Sam Wilson aka the Falcon.

When Henry Pym was debriefing Scott Lang about his mission, Lang remarked that they should call in the Avengers. Pym scoffed at the idea, claiming that they were probably too busy "dropping cities out of the sky". Later in order to ensure the accomplishment of the heist, Pym requires a device he had constructed for S.H.I.E.L.D. that lay in storage in what he knew to be an abandoned Stark Industries warehouse in Upstate New York. Ant-Man is sent in to retrieve the package only to make a unexpected discovery upon arrival that the warehouse had become The New Avengers Facility where he encounters Falcon and engages in battle against him, while managing to acquire the device.

The Avengers are in Lagos Nigeria on a mission to apprehend Brock Rumlow who now is going by the codename: Crossbones, and has been insisting terrorist attacks publicly with the aid of armed mercenaries for several months now. Cap and Black Widow take the newly recruited teammates Falcon and Scarlet Witch on the mission to prevent Crossbones from acquiring a chemical bio-Weapon from a disease control center. The team is successful in dealing with the hired mercenaries by taking them down efficiently in combat. Rumlow realizing he's outmatched goes after Captain America directly seeking revenge upon the super soldier for dropping a building upon him. Rogers fairs off well against him conturing every attack. Rumlow attempts to distract him by referring to Bucky causing disoriented focus to Steve. who unaware of a triggered suicide bomb vest by Rumlow.

Wanda tries to contain the blast of the explosion by creating a energy shield and launching it into the sky. Unfortunately the blast goes off upon a nearby building killing innocent Wakandain representatives. As a result of this international incident. The Governments of the World issue a new mandate called the Sokovia Accords satiating governmental oversight over The Avengers.

Former General Thaddeus Ross, now the Secretary of State visits the Avengers at their headquarters to deliver the accords to them and stipulates that either they sign or they retire. The Team is divided on the issue with both Tony and Steve on opposite side of disagreement regarding the ramification of the accords. Steve is against the accords because he feels this will infringe on the teams ability to be free to respond to crisis immediately. Tony is for the accords because he believes that they need to be put in check by accepting boundaries so they don't become as bad as the advisories they face.

Team Cap

Team Iron Man

The team come to blows physical in Germany at an abandoned airport : Team Cap (The Winter Soldier, Falcon, Scarlet Witch, Hawkeye and newly recruited Ant-Man). Team Iron Man {War Machine, Vision, Black Widow and two new additions Black Panther & Spider-Man} battle it out in a colossal showdown.

Behind the scenes

Joss Whedon talked about the power levels of the various Avengers: "I had to find a way to service all the characters, to figure out why they're in the room in the first place. My biggest concern was that if I didn't pay enough attention to minutiae then the film would become generic in its concepts and visuals. Or that I'd be so concentrated on those things, I'd look around and the film wouldn't be about anything."

On the action scenes and what Whedon terms "the hierarchy of power". "If this guy hits someone, he falls down. If this guy hits someone, he flies backwards. Its very complicated."

Whedon commented on Mark Ruffalo's 'Hulk' actions: "It's fun to say that Mark Ruffalo and I fought a great deal, because he's the sweetest man that I may ever have met. Yes, we did actually lay out some mats and tussle but just trying to figure out what the Hulk would be doing, what a person does in a real fight. Once he gets angry you have to keep asking "well what's making him angry now..." and go moment-to-moment. That's been the hardest thing in this movie. Mark is tremendous, I think he's going to blow people away - again - and we've gone where nobody has. We [have] Hulk in the house and everything pisses him off."

Trivia

The roster of the team is similar to that of the Ultimates roster in the comic book miniseries The Ultimates. The Ultimates were conceived as the Ultimate Marvel Universe's equivalent of the mainstream Avengers. The Avengers of the Marvel Cinematic Universe bear a strong resemblance to the Ultimates in that they were formed by S.H.I.E.L.D. as a government-sponsored team to combat the threat of the Chitauri. Like in The Ultimates 2, the team leaves S.H.I.E.L.D. employ and becomes independent.

Henry Pym (Ant-Man) and The Wasp are on the original Avengers roster in the mainstream comics, as well as their Ultimate universe versions being in the first roster of the Ultimates, but are absent from the live-action film.

The speech in the first teaser trailer was taken from the introduction of many Avengers comic books since the 1970s. In the TV series The Avengers: Earth's Mightiest Heroes, the new intro features Nick Fury stating a speech similar to this one.

The movie's roster will be seen in the next animated series Avengers Assemble with Falcon joining the roster.

With Quicksilver and Scarlet Witch appearing in Avengers: Age of Ultron, the roster continues to closely follow the comics as they both joined The Avengers along-side Captain America and Hawkeye (both of whom are founding members in the first film) after the original lineup disbanded, thus forming the second.

Unlike most of the traditional superheroes, all members of the Avengers don't have secret identities